This invention relates to current sensing in electric power supplies and, more particularly, to a flyback switching regulator wherein winding currents are monitored by a sensing of volt-seconds or flux, such monitoring being substantially free of noise associated with the operation of switching type regulators.
Many forms of power supplies have been constructed for applying power to different types of electrical loads. When regulation is required, the power supply includes a regulator circuit which senses an output current and/or voltage with control of current and/or voltage being provided, typically, by some form of feedback. One large class of regulated power supplies is the flyback switching regulator. In its usual construction, a flyback switching regulator includes input and output sections coupled by a transformer, and further comprises some form of pulsing circuit which causes pulsations of current to flow in the input section. The duration and the spacing of the input current pulses are controlled by the regulator circuit to provide a desired output voltage or current.
Some electrical loads require a regulated high voltage from a storage capacitor or pulse forming network (PFN). An important example of such load is an optically pumped laser, wherein the laser is excited by lamps which are driven by large current pulses supplied from pulse forming networks. A switching regulator power supply incorporating a flyback transformer circuit is ideally suited for providing charging current pulses to the pulse forming network. In the flyback type of power supply, current pulses appear alternately in the input and the output sections of the supply, an output current pulse being provided by the energy of an input current pulse transferred by magnetic flux of the transformer to provide the output current pulse.
A problem arises in switching regulator and flyback power supplies in that noise is produced by the switching of large current pulses (sometimes measuring in the hundreds of amperes) and is coupled into the regulator circuit by feedback signal lines from the sensors of input and output, current and voltage. In the case of lasers used in range-finding systems, such noise is coupled from the input section of the power supply to other circuitry, particularly receiver circuitry which is sensitive to noise. This results in a degradation of system performance. The noise can also degrade the performance of the regulator circuit of the power supply. Attempts to reduce the effects of the noise on the regulator circuit by filtering signals and by relocating electrical components have often not had adequate success.